Angel is the longtime collaboration of Ilpo Väisänen, probably still best known as a member of Pan Sonic, and Dirk Dresselhaus, AKA Schneider TM. Together, they produce stark, electro-acoustic, drone-based music. Terra Null., which was recorded in 2011, is their latest LP for Editions Mego, and it shows the duo joined by two other talented experimental artists: Hildur Guðnadóttir and Lucio Capece. Described as a statement on cultural Darwinism and greed, it's a challenging, tightly-controlled listen, and one that gets better (and more provocative) as you dig further in.

The appearances from Guðnadóttir and Capece are essential to the flow of Terra Null., whose hour-plus runtime is spread over four expansive tracks. Guðnadóttir, a frequent contributor to Angel releases, provides cello and vocals on the album's first three tracks. Capece, with his clarinet and saxophone, is a relative newcomer to the project, but not a stranger to this scene; his many credits include collaborations with Mika Vainio and Vladislav Delay. He gets to show his mettle on Terra Null.'s final two pieces.

The album begins with the 26-minute epic "Naked Land." Its first moments are probably the most civilized of the entire LP—there's Dresselhaus's wandering guitar lines, which wouldn't be out of place in an old western film, and a few pensive plucks of cello strings that linger to provide a bit of rhythm. Then, suffused with Väisänen and Dresselhaus's gloomy machinations, the piece moves through masses of guitar noise and effects-laden cello, drifting downward before rising up in a state of near bliss, then ending in an air of wilted melancholy. Among the many sustained sounds on "Monolake" are Guðnadóttir's clear, synchronized vocal intonations—a touch of humanity that feels almost celestial in this context.

With the addition of Capece, all four artists appear on "Colonialists." This one comes laced with descending electronic tones, but its leading feature is the combination of reeds and cellos, which make the piece sound like it's ceaselessly deflating. Lastly, and most aggressively, is "Quake," where Capece's instrumentation offers an unsteady focal point for all manner of shrieking, rumbling noise. Given the stated theme of the album, its spacious build, powerful climax and brittle, strung-out ending seem to depict the inevitable and violent collapse of an unsustainable system. I'm partial to the intense catharsis of the last two tracks, but anyone with an appetite for confrontational drones should find Terra Null. more than worth their time.